East German Pat. No. 149,845 is the only known prior art which discloses the use the surface tension/pore size relationship to control the pore size of individual holes during pore formation. This is described in relation to single sided etching of radiation tracks in polymer foil. The pores of such a foil are not connected into a foam network; they form a simple sieve. The methods disclosed in the East German Patent allow all pore diameters to be regulated by the boundary surface tension between the etching agent and an inert medium. When the pore diameter has become so large that the pressure difference between these two is sufficient to expel the etching agent from the pore, etching ceases. In theory all the pores are the same size so that the pore size distribution is monodisperse, which is not always desired.
There is a need for a method which will find every incorrectly sized pore and then individually and specifically apply a versatile treatment to it.
The known prior art has no direct relevance to the methods and products of this invention which meet this unfilled need.
The present invention differs from known art in that there is no etching nor any step related to the initial production of the pores. Instead there is alteration of existing pore size distributions in an existing porous barrier. The function of the present invention is curative not preventative of undesirable pore sizes. Often this curative approach is advantageous.